Immunology Flashcards
What is immunology?
a branch of biomedical sciences concerns with immunity or immune system
study of host defence against infection and disorders of the immune system
What is the immune system?
a complex network of organs, tissues, cells and molecules that protect the body against infections and other diseases
What are the organs and tissues of the immune system?
bone marrow
spleen
thymus
tonsils
mucous membranes
skin
lymphatic vessels
lymph nodes
What are the cells of the immune system?
lymphocytes (T-cells, B-cells and NK cells)
granulocytes (neutrophils, eosinophils and basophils)
monocytes/macrophages
What is immunity?
ability of the body to prevent invasion of pathogens (such as viruses, bacteria and fungi)
Describe innate (non-adaptive) immunity.
first line immune response (present at birth)
relying on mechanisms that exist before infections
rapid (within minutes) but non-specific
inflammation
Described acquired (adaptive) immunity.
second line immune response
T-cells and B-cells involved
developed from immunological memory
What are the cells involved in innate immunity?
natural killer cells
dendritic cells
mast cells
neutrophils
basophils
eosinophils
macrophages
What is the role of natural killer cells?
cytotoxic, kill infected cells and cancer cells
What is the role of dendritic cells?
antigen-presenting, important to acquired immunity
What is the role of mast cells?
rich in histamine and heparin, possess antibacterial and antiparasitic functions
What is the role of neutrophils?
patrol for microbial infection and one of the first responders to the site of inflammation
What is the role of basophils?
fight parasite infections and mediate allergic reactions
What is the role of eosinophils?
possess antibacterial and antiparasitic functions
What is the role of macrophages?
phagocytosis and present antigens along with dendritic cells
What are DAMPs?
damage-associated molecular patterns
-endogenous molecules released from damaged and dying cells during infection and inflammation, such as high mobility group box 1 protein (HMGB1) and heat shock proteins (HLPs)
-interacting with pattern recognition receptors (PRRs)
What is detecting missing-self?
recognizing molecules expressed in healthy cells but not in infected cells/pathogens
inhibiting innate immune response against host cells/tissues
mainly via NK cells
What is MHC?
major histocompatibility complex, essential for acquired immunity
Describe MHC class I.
HLA-A, HLA-B, HLA-C
identified in all nucleated cells
present normal self-antigens and foreign pathogen antigens to cytotoxic T cells
Describe MHC class II.
HLA-DP, HLA-DM, HLA-DOA, HLA-DOB, HLA-DQ, HLA-DR
identified in macrophages, dendritic cells and B cells
present foreign pathogen antigens to T helper cells
What is the structure of MHC class I and class II?
class I:
-heterodimer
-antigen binding pocket is on alpha unit (smaller than II)
-anchor attached to alpha unit
class II:
-binding pocket is on units and larger
-anchor is attached to both units
What are the two types of acquired immunity?
cell mediated immunity
humoral immunity
Describe cell mediated immunity.
antigen-specific cytotoxic T cells
release cytokines in response to the antigen
do not involve antibodies
kill infected cells
Describe humoral immunity.
B cells
mediated by secreted antibodies
attack and neutralize antigens outside cells
prevent microbial penetration into body cells
Where are T-cells made and matured?
bone marrow: hematopoietic stem cells –> lymphoid progenitor cells (migrate to thymus)
thymus: lymphoid progenitor cells –> functional T-cells with specific markers (such as TCR, CD4 and CD8)
Differentiate CD4 and CD8.
CD4:
-helper T cells
-secrete cytokines to stimulate the differentiation of B cells into plasma cells
CD8:
-cytotoxic T cells
-bind and kill infected cells and cancer cells
How are cytotoxic T cells activated?
activated by simultaneous interactions of surface molecules between cytotoxic T cell and APC –> T cell proliferation
first activation signal: interaction between TCR of cytotoxic T cell and MHC I molecule of APC
second activation signal: interaction between CD28 of cytotoxic T cell and CD80/CD86 of APC
What are CD80 and CD86?
co-stimulators of T cell activation
What are regulatory T cells (Tregs)?
specialized subgroup of T cells
-CD4+, CD25+, FOXP3+
-different from helper T cells
What is the role of Tregs?
supress immune response
inhibit T-cell proliferation and cytokine production
maintain immune homeostasis and self-tolerance
prevent autoimmune disease
promote cancer development and progression by inhibiting anticancer immunity within the TME
What is the role of B-cells?
provide humoral immunity
recognize specific antigens and differentiate into long-lived plasma cells
plasma cells secrete antibodies binding to specific antigens on microbes
destroy microbes and block them from entering into body cells
some B-cells evolve into memory B-cells
How are B-cells activated?
activated when B-cell receptor (BCR) binds to antigen
T-cell dependent activation
T-cell independent activation
memory B-cell activation
How are memory B-cells activated?
activated by different pathogens
differentiate into long-lived plasma cells to secrete antibodies
re-enter GCs to relinquish memory B cell pool
Describe antibodies.
belong to gamma-globulin fraction of serum proteins
Y-shaped
five classes: IgA, IgD, IgE, IgG, IgM
Describe IgA.
monomeric in serum
dimeric in GIT and respiratory tract
important first line of defence against infections
inhibits bacterial growth and neutralize bacterial toxins
neutralize viruses
Describe IgD.
monomeric
usually co-expressed with IgM
activate B-cells, basophils and mast cells
target mucosal antigens –> enhance mucosal immunity
Describe IgE.
monomeric
mediate type I hypersensitivity
provide immunity against helminth infections
Describe IgG.
~75% of serum antibodies –> main type of antibody
monomeric
produced after IgM
bind different types of antigens such as viruses, bacteria, fungi
four subclasses: IgG1, IgG2, IgG3 and IgG4
-IgG1, IgG3, and IgG4 can cross placenta
-newborns: having same Ab as mother in first 6 months
Describe IgM.
largest antibody
pentameric
first antibody produced for humoral immunity response
respond to many antigens
mainly produced from spleen and bone marrow
may also present as hexamers –> physiological function unknown
Describe mAb production via hybridoma technology.
fusion of B-cells and myeloma cells
-B cells: antibody production
-myeloma cell: longevity and reproduction
